Internet and Networking Overview

A Network is a Group of Connected Computers

Networks enable computers to share files, directories, drives and any shared resources connected to the network.

A computer that offers to share its files or resources on a network is called a Host. Other networked computers that access these shared resources are called clients.

Files are made available to other computers on a network by sharing them on the computer or server where they reside.

Files and network resources are made available to other computers on a network by a technique known as sharing. To share a file or directory means that it has been selected and then designated as a shared item. Networking software then makes the resource visible to other computers on the network. Computers that access these resources are clients.

Shared resources can also be any hardware that is networkable or is connected to a computer that offers to share the item on the network. A printer that is not otherwise networkable could be shared in this manner.

For hardware to be networkable without being connected to a host it must be capable of having an IP address assigned to it in order to be visible on the network and thus shared.

Private networks for use by businesses and individuals are called LAN (local area network). These networks can contain small or large numbers of computers. Small networks are called Peer to Peer. In a peer to peer network all computers are equal and share a dual role as both host and client. This type of network typically comprises ten or fewer computers or devices.

Large networks are called client - server networks. In this type of network the server is the host and client computers can access resources stored on or attached to the network server. Depending on scope networks that cover large geographic areas are called WAN (wide area network).

IP Address

Internet protocol addresses are used to identify computers and devices on a network and / or the Internet. All computers or devices on a LAN typically have a unique IP address (see subnet mask below for information about how to use the same IP address multiple times on the same network).

How Information Is Sent Over Networks

All data, including files, video or voice communication sent over a network is first divided into packets. The host divides data into packets and then sends these packets over the network. The client receives these packets and then reassembles them into their original form. Sending data as packets allows better utilization of networks and allows fast uninterrupted flow of information.

Common Network Types

SMB Server Message Block (a.k.a. Common Internet File System or CIFS)

SMB is a cross-platform networking scheme typically used to network computers with different operating systems such as Linux and Windows.

FTP File Transfer Protocol

FTP is a cross-platform protocol that can be used to move files between computers either on a LAN or over the Internet.

NFS Network File System

NFS is typically used for networking Linux / Unix computers.

VPN Virtual Private Networking

VPN is a cross-platform networking scheme achieved via an Internet connection.

SSH Secure Shell

SSH is a cross-platform networking scheme to enable sharing network resources as well as using computers remotely.

Networking Hardware

• Router Provides multiple connections (RJ45) to attach computers and devices to a LAN. May include NAT, DHCP, or firewall. May also have a broadband modem.
• Switch Provides multiple connections via RJ45 ports to attach computers and devices to a LAN.
• Network Adapter Interface device (either wireless or wired) used to enable computers to send and receive data over a LAN (a.k.a. NIC or network interface card).
• RJ45 Network cable connector either male or female
• Hub Obsolete, superceded by switch

Hardware and Software Firewalls

Firewalls limit the types of connections that can be made to computers or devices attached to a network. These connections are called ports, they can be simultaneously incoming and outgoing . Routers typically contain a hardware based firewall. A software firewall must be installed separately on each computer on a LAN. Firewalls provide security for protection of computers and devices attached to either a LAN or Internet.

DHCP

Dynamic Host Control Protocol is a scheme whereby a router can automatically assign IP addresses to computers or devices attached to a LAN. Network servers can also supply DHCP to a network.

Static IP

Unlike DHCP static IP addresses can be manually assign to computers or devices attached to a LAN.

NAT

Network Address Translation. Broadband subscribers are typically assigned a single IP address by their ISP. To simultaneously allow multiple computers attached to a LAN to share this IP address and thus Internet access a router with NAT will translate this single address so that each computer will appear to have a unique IP address with which to connect to the Internet.

Types of IP Addresses

There are public and private IP addresses. Private IP addresses are used to identify computers and devices on a LAN. Public IP addresses are used to identify web sites and resources available via the Internet.

In simple terms public networks are like large cities in that everyone is welcome. Private networks are like gated communities and only those with proper credentials may enter. Accessing shared resources is determined by IP address range assigned to client and IP address range assigned to host or shared resource.

Class A Public IP Address Range
10.0.0.0 through 10.255.255.255

Class B Public IP Address Range
172.16.0.0 through 172.31.255.255

Private IP Address Range
192.168.0.0 through 192.168.255.255

Localhost IP Address Range
127.0.0.0 through 127.255.255.255

Localhost is a range of IP addresses reserved for localhost communication. Localhost is a computer's own internal IP address. Addresses within this range should never appear outside a host computer and are therefore unusable for sharing resources either in public or private networks. Packets (network data) sent to this address are returned as incoming packets on the same virtual network device. This network device is known as loopback because the computer both sends and receives the same data. A loopback is used for test purposes.

Subnet Mask

A subnet mask is a method of dividing private network IP address ranges. In essence it allows networks to be categorized so that computers on the same network may communicate with other computers even though they have the same IP address.

Example of two computers with same IP address but different Subnet mask:

255.255.255.0, 192.168.1.1
255.255.255.1, 192.168.1.1

Note that both computers have identical IP address but can still communicate over the same network because they each have a different subnet mask.

Internet

The Internet is also a network. It is essentially a group of web servers. Web sites are collections of HTML files that reside on these web servers. The Internet is cross-platform. Any computer regardless of operating system can access the Internet via a web browser.

Web sites can be accessed by entering an addresses known as a URL (universal resource locator) in the address bar of a web browser. A URL is a human readable addresses. It must be translated into an IP address by a network of computers known as DNS servers (domain name servers) before a web site can be accessed by a web browser. All web site domain names represent an IP addresses. You can visit a web site either by using its domain name or its IP address.

Domain name example:
www.scroogle.org

IP address of Scroogle.org:
67.199.36.108

Registrar

A registrar is a company that registers domain names for a fee. Registrars are designated by ICANN (Internet Corporation for Assigned Names and Numbers). All domain names must be registered with a registrar.

Web Host

A web server is where web sites are stored for access over the Internet.

Web Hosting Account

Storage space on a web server that is available either for free or for a fee.

Domain Name Hosting Account

Storage space on a web server that can be configured for access over the Internet via a unique domain name.